The present invention relates to a diode-equipped microwave phase shifter capable of producing a 180.degree. phase difference and adapted to be formed as a planar structure on a ceramic substrate of high dielectric constant, more specifically to a device facilitating phase reversal by a field inversion at a junction between a slot line and a line of different field structure such as a microstrip line of the single-ground-plane or the coplanar type as disclosed in our copending application.
There are various kinds of phase shifters equipped with PIN diodes and realizable as planar structures, such as 3dB-coupler phase shifters, switching phase shifters which employ the properties of shunt T's, and interference phase shifters which employ two diodes connected in parallel to a transmission line. The number of diodes, the phase shift, the standing-wave ratio (SWR), the insertion losses and the power-carrying capacity are criteria which influence the choice of one or other of these phase shifters.
However, these prior-art phase shifters involve lengths of transmission line liable to introduce phase shifts, losses and SWR characteristics which vary with frequency.
Another conventional phase shifter known from IEEE Transactions on microwave theory and techniques, April 1976, pages 231 ff, comprises a microstrip-to-microslot transition but does not provide for a phase changeover at the junction between the two lines.